This invention relates to access openings for vehicles and more particularly to advantageous doors for semi-trailers.
Vehicles, such as semi-trailers, are generally of two types. They are either of the "roll-up" type or the "swing" type door.
The roll-up door found in trailers is similar in type to the vehicular access door commonly associated with garages. The roll-up trailer door typically is constructed from a series of wooden panels, each about one inch in thickness and twelve to eighteen inches in height. Ordinarily the panels run the width of the door opening and are held together by hinges. At opposed lateral edges of the door are a series of wheel-like rollers, known as "door rollers", which ride in vertical tracks, "door tracks", that run along the inside of the door frame, which is known as a "header". Beyond the header the door tracks extend up under the roof of the trailer. A spring mechanism helps raise the door. When the door is closed, it is held fast against the inside of the header by the track and roller system. When open, the door is stored under the roof of the trailer, supported by the door rollers and door tracks.
There is an advantage from the roll-up door because it is inside the trailer at all times. As a result, the door can be opened and closed when the trailer is at a loading dock, in an ally, or next to another trailer. However, there is the disadvantage that the roll-up door is entirely contained within the trailer. Consequently, the elevated roll-up door takes up space that could otherwise be used for cargo. For a company operating on a narrow profit margin, extra cargo space per trailer can make a difference between making money and losing money.
The second type of trailer access is provided by the swing door, which is formed by two doors mounted on hinges at the sides of the header. The doors are of a sheet-metal and plywood sandwich, and have weather stripping around the edges to prevent leakage. When closed, the swing doors are held in place by a pair of lock bars that run from the bottom of the header to the top. When the doors are opened, they swing outwardly, around the outer corners of the trailer. The swing doors can be held in an open position by small chains or other restraining devices.
Swing doors have the advantage that because they are externally mounted, the doors do not take up any room inside the trailer. This allows cargo to be stacked all the way to the roof and throughout the length of the trailer. However, swing doors have the disadvantage that they require a significant amount of room to be opened and closed. As a result, the swing doors must be opened before backing up to a loading dock. Thereafter, the swing doors cannot be closed again without pulling away from the dock. In addition, the swing doors cannot be locked in open position unless there is sufficient side clearance for the doors to swing all the way around to the sides of the trailer. Finally, when a swing door is in its locked-open position, it can be broken off if another trailer hits it.
Accordingly, it is an object of the invention to provide a single type of door that will satisfy customers for both roll-up and swing-type operation.
A related object is to provide a vehicular door that has all of the advantages of both current trailer door types, and none of their disadvantages.
Another object of the invention is to avoid the disadvantage that the roll-up door is entirely contained within the trailer. A related object is to overcome the disadvantage that the elevated roll-up door takes up space that could otherwise be used for cargo. A still another related object is to assist companies operating on narrow profit margins by providing extra cargo space per trailer, which can make a difference between making money and losing money.
A further object is to avoid the disadvantage of swing doors in that they require a significant amount of room to be opened and closed. A related object is to eliminate the need that swing doors must be opened before backing up to a loading dock with the consequence that the swing doors cannot be closed again without pulling away from the dock. Another related object is to avoid the difficulty that swing doors cannot be locked in open position unless there is sufficient side clearance for the doors to swing all the way around to the sides of the trailer. Still another related object is to overcome the difficulty that when a swing door is in its locked-open position, it can be broken off if another trailer hits it.
A further object is to retain the advantage provided by the roll-up door because it is inside the trailer at all times, so that the door can be opened and closed when the trailer is at a loading dock, in an ally, or next to another trailer.
A still further object is to retain the advantage provided by swing doors because they are externally mounted, so that the doors do not take up any room inside the trailer, allowing cargo to be stacked all the way to the roof and throughout the length of the trailer.
Still other objects of the invention include the avoidance of exterior clearance problems accompanying the use of roll-door designs; avoidance of interior cargo clearance problems; avoiding protrusion of any part of the door or door assembly outside the legal exterior dimensions for semi-trailers; avoiding intrusion of any part of the door or door assembly into the cargo space of the trailer; providing a door without significantly more moving parts than standard roll doors; and providing a door not any harder to repair than a standard roll door, be as durable as current designs, not leak in the rain and be well protected against damage done by forklifts or other trucks.